The invention relates to a method of making a paper web that exhibits high internal void volume from a furnish having a substantial amount of ash, fines and/or secondary fibers. More particularly, the invention relates to a method for making a near-premium quality strong and soft paper web from inexpensive secondary fibers that contain high levels of ash and fines. Still more particularly, the present invention relates to a paper product made according to the present invention. Further, the present invention relates to a method of making a paper web having improved softener retention and/or strength-adjusting agent efficiency. Finally, the present invention relates to a method of making an embossed paper product with conventional and mated embossing and an undulatory crepe blade to make a softer, thicker web with higher cross-directional stretch.
The current market for products made from soft absorbent paper webs has long been split between premium products and economy products. Commercial paper toweling, dispenser napkins and single-ply tissue products are often relegated to the economy value market because they have often been made from inexpensive recycled fibers resulting in thin and/or rough products, often having poor absorbency. It was heretofore difficult to make soft absorbent paper webs having sufficient strength, softness and absorbency to qualify as premium or near-premium quality without resorting to more expensive virgin fibers and/or expensive processing methods.
Through air drying (TAD) has changed the industry""s ability to produce soft, bulky, premium quality paper products, particularly in the area of single-ply products. TAD has become the preferred choice for newly purchased paper machines because it can provide improved product attributes and therefore, economic advantages to manufacturers when compared with the products produced by conventional wet pressing (CWP). The advent of TAD has made it possible to produce paper products with good initial softness and bulk.
In the older conventional wet pressing method, premium quality paper products, tissues and towels, are normally made by embossing together two thin plies. In this way, the rougher air-side surfaces (i.e., those surfaces not previously in contact with the surface of the Yankee dryer) can be made to face inward, thereby being concealed within the two-ply sheet. However, embossing two-plies together imposes marked economic disadvantages over single-ply paper TAD sheets.
Conventional wet pressing, however, has certain advantages over TAD including 1) lower energy costs associated with the mechanical removal of water rather than drying by the passage of hot air; and 2) increased production speeds. Stated differently, energy consumption is lower and the production speeds can be considerably higher than those used in TAD.
Conversion of existing CWP machines to TAD capability is both difficult and expensive. What is needed is a method of making premium quality, or near-premium quality paper products using conventional wet pressing from recycled fiber. More preferably, a premium quality or near-premium quality two-ply and even more preferably a single-ply product should be produced from inexpensive and recycled fibers without the need for significant preprocessing of the fibers to remove ash and fines.
Attempts have been made to produce products from recycled fiber using CWP that can compete with TAD products, but these processes often suffer from limitations making it necessary to use more expensive virgin fibers to achieve an acceptable product. One common method of increasing the softness and cushion of bathroom tissue is to crepe the paper. Creping is generally accomplished by fixing the cellulosic web to a Yankee drier with an adhesive/release agent combination and then scraping the web off the Yankee by means of a creping blade. Creping, by breaking a significant number of inter-fiber bonds, adds to and increases the softness of resulting bathroom tissue product. However, creping with a conventional blade may not provide the most preferred combinations of softness, bulk and appearance.
According to one preferred embodiment of the present invention, we have discovered that tissue having highly desirable bulk, appearance and softness characteristics, can be produced by a process similar to conventional processes, particularly conventional wet pressing, except that the conventional creping blade is replaced with the patented undulatory creping blade disclosed in U.S. Pat. No. 5,690,788,1 presenting differentiated creping and rake angles to the sheet and having a multiplicity of spaced serrulated creping sections of either uniform depths or non-uniform arrays of depths. The depths of the undulations are above about 0.008 inches.
1U.S. Pat. No. 5,690,788 is herein incorporated by reference in its entirety. 
The present invention makes it possible to use inexpensive secondary fiber that may contain significant amounts of ash and fines and yet, achieve a premium or near-premium quality paper product. The paper products made according to the present invention exhibit characteristics approaching the much more expensive TAD products. Moreover, products made using the patented undulatory blade to crepe the web will have a crepe fineness similar to that of conventionally-made tissue sheets, but the resulting web combines crepe bars extending in the cross direction with undulations extending in the machine direction. The resultant product will have a lower tensile strength and a higher caliper and cross-directional stretch than is found when using a conventional crepe blade.
Further advantages of the invention will be set forth in part in the description which follows and in part will be apparent from the description. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is disclosed:
A method for forming a soft absorbent paper product including,
supplying an aqueous stream including fibers to form a furnish;
adding a charge modifier to the furnish where the charge modifier contacts the furnish for a time sufficient to reduce the charge in the furnish;
adding a debonder or wet strength adjusting agent to the furnish, after the charge has been reduced;
adding a retention aid to the furnish after the debonder or wet strength adjusting agent has been in contact with the furnish for a time sufficient to allow distribution of the debonder or wet strength adjusting agent on the fibers;
supplying the furnish to a headbox, and where the furnish has a consistency of not greater than 0.9% as supplied to the headbox;
applying the furnish to a forming wire and forming a nascent web; and
drying the web to form a paper product.
There is further disclosed:
A soft absorbent paper product comprising a web formed by conventional wet pressing of a cellulosic web, adhering the web to a Yankee and creping the web from said Yankee including:
fibers including secondary fibers having at least 1% ash;
and wherein the web has a void volume of:
void volumexe2x89xa78.4xe2x88x92(0.2xc3x97Basis Weight).
There is still further disclosed:
A soft absorbent paper product comprising a web formed by through air drying comprising:
fibers including secondary fibers having at least 1% ash;
and wherein the web has a void volume of:
void volumexe2x89xa78.4xe2x88x92(0.2xc3x97Basis Weight).
There is also disclosed:
A method for improving the retention of a softener or debonder in a web produced from a furnish containing contaminants selected from ash, fines, filler and mixtures thereof including:
adding to the furnish a charge-modifying agent capable of neutralizing the charge on the contaminants;
allowing the charge-modifying agent to contact the furnish for a time sufficient to neutralize charge on the contaminants;
adding to the furnish a softener or debonder;
adding to the furnish a retention aid;
forming a nascent web from the furnish; and
drying the web.
There is still further disclosed:
A method of incorporating ash or filler into a soft absorbent web including;
providing a furnish containing ash or filler;
adding to the furnish a charge modifier capable of neutralizing charge on the ash or filler;
allowing the charge modifier to contact the furnish for a time sufficient to neutralize charge on the ash or filler;
adding to the furnish a debonder or wet strength adjusting agent;
adding to the furnish a retention aid;
forming a nascent web from the furnish; and
drying said web.
Further there is disclosed:
A method for improving the efficiency of a strength-adjusting agent in a web produced from a furnish containing contaminants selected from ash, fines, filler and mixtures thereof including:
adding to the furnish a charge-modifying agent capable of reducing the charge on the contaminants;
allowing the charge-modifying agent to contact the furnish for a time sufficient to reduce the charge on the contaminants;
adding a strength-adjusting agent to the furnish;
adding a retention aid to the furnish;
forming a nascent web from the furnish; and
drying the web.
There is still further disclosed:
A method for forming a soft absorbent paper product including,
supplying an aqueous stream including fibers to form a furnish;
adding a charge modifier to the furnish where the charge modifier contacts the furnish for a time sufficient to reduce the charge in the furnish;
adding a debonder or wet strength adjusting agent to the furnish, after the charge has been reduced;
adding a retention aid to the furnish after the debonder or wet strength adjusting agent has been in contact with the furnish for a time sufficient to allow distribution of the debonder or wet strength adjusting agent on the fibers;
supplying the furnish to a headbox, and where the furnish has a consistency of not greater than 0.9% as supplied to the headbox;
applying the furnish to a forming wire and forming a nascent web; and
drying the web to form a paper product;
where the drying step comprises:
compactively dewatering the nascent web;
applying the web to a Yankee drier and drying the web; and
creping the web from the Yankee drier at a moisture content of less than 50%;
where the web is creped using an undulatory crepe blade which produces the absorbent paper product, the web having a machine direction and a cross-machine direction and the web having a Yankee side and an air side, comprising a biaxially undulatory cellulosic fibrous web characterized by a reticulum of intersecting undulation and crepe bars, the crepe bars extending transversely in the cross-machine direction, the undulation defining:
interspersed ridges and furrows extending longitudinally in the machine direction on the air side of the sheath;
along with interspersed crests and serrations disposed on the Yankee side of the web, wherein the spatial frequency of the transversely extending crepe bars is from about 8 to about 150 crepe bars per inch, and the spatial frequency of the longitudinally extending ridges is from about 8 to 50 ridges per inch.